Re: [PATCH v2 2/2] watchdog: s3c2410_wdt: use exynos_get_pmu_regmap_by_phandle() for PMU regs

Hi Sam & Saravana,

On Tue, 30 Jan 2024 at 03:38, Sam Protsenko [off-list ref] wrote:

On Mon, Jan 29, 2024 at 4:25 PM Saravana Kannan [off-list ref] wrote:

quoted

On Mon, Jan 29, 2024 at 1:19 PM Peter Griffin [off-list ref] wrote:

quoted

Obtain the PMU regmap using the new API added to exynos-pmu driver rather
than syscon_regmap_lookup_by_phandle(). As this driver no longer depends
on mfd syscon remove that header and Kconfig dependency.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
---
 drivers/watchdog/Kconfig       | 1 -
 drivers/watchdog/s3c2410_wdt.c | 9 +++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 7d22051b15a2..d78fe7137799 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig

@@ -512,7 +512,6 @@ config S3C2410_WATCHDOG
        tristate "S3C6410/S5Pv210/Exynos Watchdog"
        depends on ARCH_S3C64XX || ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST
        select WATCHDOG_CORE
-       select MFD_SYSCON if ARCH_EXYNOS

That reminds me: now that exynos-pmu driver uses regmap API, does it
make sense to add something like "select REGMAP" to EXYNOS_PMU option?

Good point, I will add that in v3.

quoted

quoted

        help
          Watchdog timer block in the Samsung S3C64xx, S5Pv210 and Exynos
          SoCs. This will reboot the system when the timer expires with

diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
index 349d30462c8c..a1e2682c7e57 100644
--- a/drivers/watchdog/s3c2410_wdt.c
+++ b/drivers/watchdog/s3c2410_wdt.c

@@ -24,9 +24,9 @@
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/of.h>
-#include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
 #include <linux/delay.h>
+#include <linux/soc/samsung/exynos-pmu.h>

 #define S3C2410_WTCON          0x00
 #define S3C2410_WTDAT          0x04

@@ -699,11 +699,12 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
                return ret;

        if (wdt->drv_data->quirks & QUIRKS_HAVE_PMUREG) {
-               wdt->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,
-                                               "samsung,syscon-phandle");
+
+               wdt->pmureg = exynos_get_pmu_regmap_by_phandle(dev->of_node,
+                                                "samsung,syscon-phandle");

This looks so much better than approach taken in v1, as for my taste.
For this patch:

Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>

Thanks!

quoted

IIUC, the exynos PMU driver is registering a regmap interface with
regmap framework. So, can't we get the remap from the framework
instead of directly talking to the PMU driver?

I'm not aware of any existing regmap API that does that. A quick look
through regmap code I can't see any global state that is stored on a
regmap_init() for example of all the regmaps created in the system.

As Sam mentions below, prior to these patches the syscon device would
be creating the PMU mmio regmap and consumers drivers would be
obtaining the regmap by going through the syscon driver. After this
series we instead talk to the exynos-pmu driver to obtain the pmu
regmap which can either be one with overridden operations for issuing
SMC calls to do the register accesses or still a mmio regmap.

Folks tried in the past to add a SMC backend to regmap similar to
regmap_mmio and add support for it into syscon driver but this was
nacked (see here
https://lore.kernel.org/lkml/20210723163759.GI5221@sirena.org.uk/T/ (local))

Peter is basically re-implementing syscon driver with overridden
operations, as a part of exynos-pmu driver, in previous patch. Which
means syscon API can't be used anymore to obtain the regmap. Do you
have particular API in mind that allows getting a random regmap
registered with devm_regmap_init()?

Thanks,

Peter

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